In Building Information Modeling (BIM), various tools are used throughout various BIM phases such as architecture design, construction, simulation, and operations, and others, in generating electronic or digital representations of physical and functional characteristics of a facility or building and managing them. Each tool used in one or more of those phases has its own file and data format. There is no standard other than Industry Foundation Class (IFC), and for the most part, no interoperability among the tools. BIM Tools and File formats used by BIM tools, e.g., include design tools such as Autodesk AutoCAD™ using .DWG and .DWF formats, Revit™ using .RVT and .RFA formats, Google™ Sketchup using .SKP format, simulation tools such as EnergyPlus, an energy simulation tool using .IDF format, Radiance, a lighting simulation tool using .RAD format, CONTAM, an airflow/contaminant simulation using .PRJ format. For the BIM life cycle, all those different kinds of file formats need to be supported. However, no interoperability between various BIM tools of different phases of the BIM Lifecycle
Moreover, little has been done to convert architecture design IFC file format to EnergyPlus (.IDF) file format, which is used by one of the popular energy simulation tools, i.e., EnergyPlus. One of the reasons is that it is quite complex both on the input and the output sides. For more description of EnergyPlus, see, http://appsl.eere.energy.gov/buildings/energyplus/energyplus_about.cfm. (note the blank spaces are added in the URL so that the text does not automatically convert to a hypertext link, in order to comply with the USPTO requirement that the specification does not contain an embedded hypertext).
On the input side, there are complexities in processing the input files. First, the architecture design files in IFC or in IFCXML, which can be converted from an IFC file using existing conversion tools, are huge and very difficult to parse. An average size of IFC file could be several hundreds of Mega bytes. Conventional desktop computers are limited with memory and central processing unit (CPU) power and unable to read in the entire file and keep it in the memory to query the elements, e.g., parsing using DOM parser for IFCXML files. Instead, the files must be parsed in an iterative way. What makes the matter more complicated is the enclosing IFC element that references the smaller or atomic elements often defined after the smaller or atomic elements, which are defined first in the files. Therefore, multiple passes of parsing must be executed to finally obtain the value in the targeted atomic elements.
On the output side, there are other complexities too. In the building domain, multiple representations of a building object are possible. Intelligence is required to select only those necessary objects required by the simulation tools for an area, e.g., energy simulation. Unnecessary objects in the output file can potentially increase the size of the file, and consequently, increase the computational time and resources significantly while adding no value to the simulations. In addition, data needs to be transformed and translated to be used by the simulation tools. Furthermore, it is difficult to identify the necessary mapping from the Model View Definition (MVD) to create the necessary the translation and transformation functions for a target simulation tool, e.g., EnergyPlus for energy simulation and Radiance for lighting simulation
In summary, architectural design files (e.g., IFC) have different file formats from the files that simulation tools use, e.g., energy simulation files as such EnergyPlus IDF files. Currently, EnergyPlus IDF files can be manually created for EnergyPlus to use. However, this manual process is time consuming and requires significant domain knowledge in both the simulation areas, e.g., energy simulation and/or lighting simulation, as well as the simulation tools, e.g., EnergyPlus and/or Radiance. In an example of a classroom setting, an estimated 100 hours per student was spent in using the data in architectural design file in IFC to manually create an .IDF file for use by EnergyPlus to run energy simulation. Hence, current manual efforts in translation and transformation input files and producing output files for numerous different building information models are both difficult and inefficient. Moreover, there is no automated way to extract data to create energy simulation files.